Process of tanning hides.



No. 651,935. Patentedlune 19, |900.

A. H. SCHMIDT.

PROCESS `0F TANNING HIES.

Application led June 15, 1899.\ v (No Model.)

UNITED STATES PATENT OFFICE.

AUGUSTHERMANN SCHMIDT, OF HAMBURG, GERMANY.

PROCESS OF TANNING HIDES.`

SPECIFICATION forming para of Lettersratent No. 651,935, dated June 19, 1900. Application led June 15, 1899. Sierial No. 720.637. (No specimens.)

To @ZZ whom it may concern:

Be it known that I, AUGUST HERMANN SCHMIDT, a citizen of the free and Hanseatic town of Hamburg, in the German Empire, have invented a certain new and useful Proc# ess of Tanning Hides, of which the following is a specification. l

My invention relates to a process for tan: ning hides whereby the tanning solution, in conjunction with oxygen or air, is caused to act upon the bated and depilated hides, there# by effecting a more rapid process and better leather.

I have found that tannins in the presence of oxygen split up and form products whose exact chemical composition is not known, but which have a most benecial and rapid tanning action on the hides, especially in the early stages of the process, when they penef trate the hides with the greatest ease; c

The hides or skinsare raised or swelled pre# vious to my tanning process, which can be done in accordance with' any of the methods usually employed, as by means of Water acidulated with sulfuric acid or similar solutions. This swelling or raising loosens all the fibers of the corium and allows the products due to the action of the oxygen on the tan liquor to penetrate into the hide or skin. If this swell# ing or raising were not done, the aforesaid tannin products would not penetrate the hide or skin, but form a crust on or in the outer iibers and prevent any further penetration or absorption. As the tan liquor or ooze is in contact with the hides during the tanning process and has an astringent or shrinking action on the fibers, it is best, in order to effect a thorough penetration of the products of decomposition, to treat the depilated and bated hides iirst with a weak solution of tan liquor in conjunction with a gas rich in oxygen, as air enriched inoxygen or ozone, so as to cause at this stage the most active formation of decomposition products of the tanning before the fibers of the hide or skin have shrunk or contracted too much, which would be the caseif. a strong solution oftanf nin were used at this time, thereby prevent,- ing the formationl of an impermeable deposit or crust on the surface of the hides.

By air rich in oxygen or ozone l mean air containing from two to three times the normal proportion of oxygen or ozone.

Inasmuch as the astringent action of the tanning liquor upon the hides depends upon thel degree of concentration of such liquor andin order to avoid too greata contraction f the hides in the start and at the same time promote the formation 'of thesplit products referred to and enable them to more readily penetrate into the raised or swelled green hides, I use in the start a weak tanning solution and a gas or air rich in oxygen or ozone, as above set forth.

The green hides are kept in motion in a confined space in a revoluble drum half-filled with tan liquor and hides, the other half of the drum being filled with air rich in oxygen or ozone. The great amount of oxygen or ozone acting upon the constantly-agitated tan liquor in contact with the hides oxidizes theformer, split products in large quantities being formed, which readily e penetrate the hides. After the hides have been exposed to the action of thesesplit products, say, for fromabout four to six hours, according to texture and weight, the tan liquor is removed, and fresh and more concentrated liquor is introduced into the drum in such a manner as not to allow the air therein to escape. e about one-half of its oxygen in the first stage, the oxidizing action of the air on the tan liquor is correspondingly reduced, while the actionv of the stronger tan liquor on the hides is correspondingly increased, resulting in a further contraction or shrinking of the hides lor skins, with a reduction in the proportion 'of split products. After4 the hides have been exposed to the action of the stronger liquor and to the action of the split products formed for a sufficient length of time-say for about eight hoursthe tan liquor is againremoved and a stronger liquor supplied to the drum. During the second stage the air will have been deprived of about two-thirds of its oxygen or ozone,- so that the formation of ,split vproducts during the third stage is still furation of tanning being completed during this Inasmuch as the air has given up i IOO It will thus `bessen that the action of the tan-` ning agent upon the hides is successively increased, while the formation of split products is successively-reduced. Y

The strength of the tanning liquor at each of the above-described stages of my process will naturally vary in accordance `with Vthe texture and weight of. the hides or'skins 'to' be tanned. "lhus, for instance, in tanning hides or skins of finer texture and of moderate weight the tanning liquor used in the first stage may have a strength of 1o Baume, more concentrated liquor being used for the second and Athird stages, as liquors of from 2 to 4 Baume, while about sixty gallons of air rich` in oxygen or ozone to every square foot of .hide or skin is required.

I-nvie'w of4 the peculiar -mode of carrying o ut my invention the process is readily appli- Cable to a continuous operation, as will hereinafterappear. Y

In order that the nature of the invention may be more fully understood, I will now describe the same in detail, reference being had to the accompanying drawing, which illustrates in section the preferred form of apparatus suitable for the purpose.

i Similar letters of reference refer to like pifiS; *y

The apparatus consists of Ia series of vessels-say Vfour drums A B C D-to each ofH which l issecured a gear-whe'el K K2 K3 K2 respectively 1adapted to be driven by pin` ions on fa belt-driven line-shaft or otherconvenient means. (Not shown), The drums receieve a slow rotary motion and are supplied fromasuitable tank', M by `means of a main feed-pipe E, having branch pipes `e e2 eis e4, inlet connections d d2 d3 d4, and centralj nozzles a t2 `a2 a4, while the tanks discharge through similar fnozzles b' b2 bs b4 and outlet connection-sg g2 g3 g4 into a common outletpipe VL.` By this means the drums can ybe only half-filled with tan liquor, while the remaining space `is lled with air 'having a greater or less percentage of oxygen, according -to the weight and size of the skins or hides.` The wooden walls of the cylindrical drums are furnished with pegs z z2 .z5 Z4, respectively, which during the rotation of the drums repeatedly lift the soaked skins out of the liquor and expose them to the action of the oxygen of the air contained in the drums and finally allow them to drop back into the tan liquor. One fof the four drums shownis supposed to be discharging and recharging while the others are in operation, and we will consider that the drum A is stationary 'for this purpose and that the drums B C D` are in operation. The drums are rotatably mounted in suitablestandards H' J H2 J 2 H8 J? H4 J4. Of these three drums the -d-ru'm- B is the mostv advanced, the drum C the next, and the drum D is the one last charged. The introduction of concentrated liquor is effect'- ed by closing the inlet-valves Q Q3 QiNand opening the valve Q2 ofthe drum B and also the valve -Z of the tank M.v The liquor from the tank then iiows through the main pipe E, branch pipe e2, Valve Q2, connecting-pipe d2, and .hollow pivot a2 into the drum B, where We have a strong solution of tan liquor flowing into said drum, which in the last stage of `the process `is exhausted of the greater part of the oxygen therein, thus allowing mostly tannin itself -rather than its decomposition products to act on the hides contained therein. From this drum the weakened liquor,

, say, of mean concentration runs oit through the outlet-nozzle h2, connecting-pipes g2 ha, valve R5, pipe d3, and nozzle `ai" into drum C i-n ya continuous stream, where we have a liquor of mean concentration, .an-'atmosphera say, of mean concentration i-noxyge-n, and

hides in the middle stage or second period of the tanning process and where the latmosphere is being depleted of its oxygen and the tan liquor of its tannin.y The liquor leaves the tank C through pivot bconnections g3 g4, and valve R4, pipe d4, inlet-nozzle a4, and en-ters the drum D a'weakliquor, where it comes in contact with h-ides 4just raised er swollen and van atmosphere rich in oxygen. The liquor leaves this tank by nozzle b4, pipe g4, valve T, and pipe 'm4 into the exhaustpipe L and may then be used for'oth'erpu-rposes, but is too poor in tannin l`for -further use `in-this process. f I

When the skinsin the dru-m B are tanned, it is stopped for discharging, while the 'drum A, which has just been charged, is put ,into service and the strong :liquor'from tank M is caused to pass through the mai-n pipe E, branch pipe e3, valve Q3, 'connecting-pipe d3, and hollow pivot 0,8 into the dru-rn C., from which it flows,n1ed.iumly concentrated, as above described,fi1nto drum D and thence through nozzle b4, `pipe fg?, return-pipe U through the open valves W and V therein,

A-pipe h', valve R', pipe fd', and 4nozzle a into drum A a weak liquor, and after vexhaustion it is discharged through vthe' nozzle 1)',pipe g., valve S', and pipe m intothe dischargepipe L. f

When it is desiredl to discharge the .liquor from `any one drum,-compressed ai?!` from an air-pipe G is allowedto enter the :main pipe E by opening the valve N, and thus permit the air to pass to such drum and -force out the liquor. j

. My improved process lenables me to Vproduce a leather tougher andof a I'better quality than that Vproduced bythe quick processes now in use and even better than that produced by the lengthy pit-tanning.

Having thus `described lmy invention., what I claim -as new therei-n,-and desire *to secure by Letters Patent, is'- loo IZO

l. In the art ottanning, the process which consists in subjecting batcd and depilated skins to the action of atan liquor of increasing strength and to an atmosphere decreasing in its content of oxygen, substantially as described.

2. In the art of tanning, the process which consists in subjecting hated and depilated skins to the action of a Weak tan liquor and an atmosphere strong in oxygen, concentrating the liquor during the tanning and decreasing the amount of oxygen, substantially as set forth.

3. In the art of tanning, the process which consists in subjecting the skins to the action of a weak tan liquor and to the action of an atmosphere rich in oxygen, then subjecting said skins successively to the action of tan'liq uors of correspondingly-increasing strength and to the action of an atmosphere correspondingly poorer in oxygen, said skins being exposed to the action of the tan liquor and to that of the oxygen alternately during said operation, substantially as set forth.

4Q In the art of tanning, the process which consists in subjecting bated and depilated hides to the simultaneous action of a tanning liquor of gradually-increasing strength and an atmosphere containing oxygen, the proportion of oxygen in the atmosphere diminished as the strength of the tan liquor increases, substantially as set forth.

AUGUST HERMANN' SCHMIDT. Witnesses:

ALEXANDER SPECET, Y ERNEST H. L. MUMMENHOFF. 

